As processing steps executed after circuit patterns are formed on the surface of a semiconductor wafer, those shown in Japanese Patent Publication (Unexamined) H5-63077, for example, have been proposed heretofore.
The processing steps executed after the circuit patterns are formed include a back grinding step for cutting and grinding the back of the wafer to a required thickness, a dicing step for cutting and dividing the wafer into individual elements, and so on. Since the wafer undergoes mechanical stress in each of these steps, a separate step is provided for applying adhesive tape to the surface of the wafer to protect the circuit patterns on the surface of the wafer and fix the wafer in position.
The flow of these steps is approximately as follows. First, in the back grinding step, (1) a protective adhesive tape is applied to the surface of the wafer on which circuit patterns are formed. (2) After the wafer surface to which the protective adhesive tape has been applied is supported by a suction member and the wafer is fixed in position, its back is cut and ground. With the protective adhesive tape applied to the wafer surface, the next, adhesive tape applying and peeling steps are executed. (3) The protective adhesive tape on the surface of the wafer is peeled after a supporting adhesive tape having strong adhesion is applied to the back of the wafer and the wafer is mounted in a ring-shaped frame by means of this supporting adhesive tape. In the next dicing step, (4) the wafer is cut and divided into individual elements by a diamond cutter rotating at high speed.
Through the above flow of steps, the process after the circuit patterns are formed on the semiconductor wafer surface is performed. Details of the above step (3) for peeling the protective adhesive tape from the wafer surface will be described with reference FIGS. 25 through 27. First, as shown in FIG. 25, a wafer W mounted in a ring-shaped frame F by means of supporting adhesive tape 1 is suction-supported on a suction table 2. A draw roller 6 and a pinch roller 7 on which a peeling tape 5 drawn from a supply source not shown is wound, and an applying roller 8, are arranged slightly above a peel starting end 3a of protective adhesive tape 3 applied to the surface of wafer W. Next, as shown in FIG. 26, the applying roller 8 is lowered and biased to said peel starting end 3a to bond the peeling tape 5 and protective adhesive tape 3 together. Then, as shown in FIG. 27, the pinch roller 7 is lowered to the draw roller 6, and the three rollers 6, 7 and 8 are moved in the direction of a peel finishing end 3b ( afterward in FIG. 27). At this time, the applying roller 8 moves while pressing the peeling tape 5 on the protective adhesive tape 3, and the draw roller 6 peels the protective adhesive tape 3 by means of the peeling tape 5.
However, the above step of peeling the protective adhesive tape has the problem set out below. That is, when the applying roller 8 is lowered and biased to the peel starting end 3a to bond the peeling tape 5 and protective adhesive tape 3 together, since, as is well-known, the wafer W is very thin, with the thickness approximately 110-450 .mu.m, as shown in FIG. 28, for example, the supporting adhesive tape 1 exposed adjacent the peel starting end 3a of protective adhesive tape 3 and the peeling tape 5 lowered and biased by the applying roller 8 from above the peel starting end 3a have adhesive surfaces thereof stick to each other. When the three rollers 6, 7 and 8 are moved in this state to continue the peeling operation, the wafer W undergoes bending stress and the wafer W could crack.
To avoid the above inconvenience, as shown in FIG. 29, for example, the applying roller 8 may be lowered and biased slightly inwardly of the peel starting end 3a of protective adhesive tape 3 in the direction of the center of protective adhesive tape 3 to bond the peeling tape 5 and protective adhesive tape 3 together. Then, the peeling tape 5 is not applied to the peel starting end 3a of protective adhesive tape 3. The protective adhesive tape 3 cannot be peeled smoothly when the three rollers 6, 7 and 8 are moved in the direction of the peel finishing end 3b (leftward in FIG. 29).
This invention has been made having regard to the state of the art noted above, and its object is to provide a method and apparatus for peeling a protective adhesive tape from a semiconductor wafer reliably, without a peeling tape and a supporting adhesive tape applied to the back of the wafer sticking to each other.